Detection of Bacillus cereus and Pseudomonas fluorescens in dual-species biofilm via real-time PCR and eradication using grapefruit seed extract

Foodborne outbreaks are closely associated with the formation of biofilms. However, due to their complexity of the formation and structure, studies of dual-species biofilms are still required. The aim of this study was to analyse the dual-species biofilm of Bacillus cereus and Pseudomonas fluorescens by investigating the interactions between the two species. The results showed that the dual-species biofilm had a higher amount of protein than the mono-species biofilms of the two bacterial species. In addition, in mono-species and dual-species biofilms, the number of B. cereus and P. fluorescens was shown to increase and decrease, respectively, over time. With respect to antimicrobial resistance, the dual-species biofilm required a higher amount of grapefruit seed extract (GSE) than the mono-species biofilms, indicating that the resistance of dual-species biofilm was higher. As only a limited number of studies have investigated the interactions between B. cereus and P. fluorescens using real-time PCR and adopting GSE as an antimicrobial agent, this study may assist the food industries in controlling dual-species biofilms that contain these two bacterial species.